IT WAS always going to get dirty, but no one expected it to descend into a festival of such venomous acrimony quite so quickly. There are, after all, five weeks of this Euro bloodfest still to go.

Lord Heseltine, the wily old Tory grandee, wins this week’s silver stiletto award after plunging his metaphorical dagger into the Eurosceptic chest of Boris Johnson, branding the former London mayor’s campaign remarks not only “preposterous” but “obscene”. 

Then, David Cameron popped up in the gilded splendour of the City of London’s Mansion House to tell an audience of powerbrokers the only people who would be punching the air if Britain left the EU were Russian president Vladimir Putin and Islamic State.

Needless to say, the Leave camp was incensed. It was particularly irate after a leaked letter suggested the Prime Minister had secretly connived with the leaders of big business to block Brexit.  

The development prompted Mr Johnson to declare, in his characteristically idiosyncratic way, that this was the “biggest stitch-up since the Bayeaux tapestry”.

No 10 allegedly considered calling in PC Plod over the leak. A Whitehall source noted the Serco letter was “about prisons; draw your own conclusions”. The secretary of state in charge of prisons is – Michael Gove, the leading Brexiteer. The Ministry of Justice strongly denied any involvement by the Scot.

The Queen’s Speech was memorable for its immemorability. The much-vaunted Sovereignty Bill failed to make an appearance because Mr Cameron did not want to highlight the need for one; it would have made Vote Leave’s point for it.

Steve Baker, co-chairman of Conservatives for Britain, then pointed the finger at No 10 as being the engine room behind “vicious briefing” against leading Leave figures. Whatever gave him that idea?

The next day, it emerged 25 Eurosceptic Tories were planning to side with Labour and the SNP to vote down the Queen’s Speech on an amendment, expressing concern at the privatisation effect of the proposed US-EU TTIP trade deal on the NHS. 

In a bid to head off a possible humiliating Commons defeat, Downing St announced it would accept the amendment. Vote Leave accused it of a humiliating U-turn but No 10 simply shrugged its shoulders, pointing out how the NHS was now protected under TTIP.

Two other interesting developments happened in a week of Euro-frenzy. Firstly, a poll gave Remain its biggest lead of the campaign, 18 points. With 20 per cent of voters still to make up their minds, most of whom are likely to stay with the status quo, Vote Leave has its work cut out.

Secondly and reaffirming this point, bookmakers William Hill slashed its odds on a Remain victory to 2/9 on.

The PM might want to avoid a “Tory pyscho-drama” by not debating Messrs Johnson and Gove on the telly, but once his blood-stained party emerges from the EU battle, it will be difficult to heal the wounds any time soon. The repercussions could linger long and hard for the Conservative government, whether Mr Cameron stays or goes.